V2Rocket

The last few days I've noticed that the first time I start my car each day it will crank over fine, fire for a second, stumble really low and then idle fine right afterwards. I can shut the car off and start it again and its fine.

This happened one time before and I figured it was low fuel pressure as the car had sat for a few days.

Am I right? Or is something else wrong?

black944 turbo

I think this is a common problem, no help here though

V2Rocket

just to clarify a few things:

ignition coil is new
DME relay is new
DME is stock that came with the car but has never had problems before
engine was rebuilt 2 years ago top to bottom
injectors were rebuilt 2 years ago
spark plugs are at most a month old
plug wires were replaced 2 years ago
air filter is maybe a month old
fuel pump is used but tested good less than a month ago

ibkevin

Needs a SC..

Early cars have an off-idle stumble, are you sure this is the first time you noticed it?

V2Rocket

i know the regular stumble when you drop the throttle, it falls below idle for a second and then catches up.

this is immediately after the car cranks though, no throttle input at all.

the first time this happened was maybe a month ago, (about the time i took it to riverside) then it didnt happen until a few days ago and has happened every time since. the car has been getting alot of mileage lately (ive been driving to/from la jolla just about every day since last sunday) so im wondering if that has anything to do with it.


but yes, i agree, it needs that SC bad. soon my friend soon.

ibkevin

Check TPS connection?

potent951turbo

Have you checked out your AFM?

Wallace

Could be Fuel Pressure Regulator or Fuel Pressure Damper.

Pull the vacuum line off each and check for fuel (smell for fuel as well).
If there's fuel in either vacuum line, replace both, as they often fail around the same time.

Mongo

Auxiliary Air Valve. Enough said. My '84 944 with 183,000 miles back in late 2003 started doing the same thing. The valve has become dirty with dust or a small buildup. You can shoot some WD40 into the vacuum line there if you can get a small tube that you can insert the WD40 straw into.

athens944

I would check the spark plugs. Did you replace them with a different version? Gapped properly? Torqued properly?

V2Rocket

will do.
should be good still, took it apart maybe a year ago and everything looked alright. maybe the track's worn out...oh well, i have like 3 spares (maybe time to switch to later model )
oh noooo..i hope not. sounds expensive.
same plugs ive run since rebuild, bosch platinum +2. i know i know platinum is less conductive than copper but ive never had problems with these ones and they look pretty.
pardon my ignorance, but is that the funky lumpy thing that bolts onto the block and is hidden away underneath the intake manifold?

Andy1212

Yea it is, but i can almost guarantee thats not your problem. I think its the AFM as well.

John_AZ

Could be as simple as the fuel check valve at the exit of the fuel pump.
Tiny ball and spring keeps fuel lines pressurized. Your symptoms sound like it is dirty or needs replacement.

John_AZ
1988 924S + 1987 924S

Will Feather

I get the same problem sometimes. I always assume its probably a fuel pressure issue. It only happens after the car has been sitting a little while, and only on that first start up.

ArcticSteve

Auxiliary Air Valve is my vote. I used carb cleaner two years ago and fixed the idle stumble on day old startups. I just got the 924S out for the first time and the same stumble is back just a bit so I'll be giving it another blast.